The present invention relates generally to microwave radiation detectors and means for indicating the presence of microwave sources. Typically a microwave oven employs a magnetron tube and a power supply consisting of a high voltage transformer and a diode rectifier. The power is not filtered and pulse modulates the magnetron on and off. The microwave fields leaking from the microwave ovens can therefore be measured by simple receivers comprised of antennas, rectifying diodes, amplifiers and indicating devices. The commonly used indicating devices consist of current or volt meters which are relatively large and costly mechanical devices having a limited dynamic range and requiring some degree of skill to correctly interpret the indication. Most owners of microwave ovens therefore do not have means for checking the leakage of their oven.